Experiments on anisotropic radial viscous fingering

We observe dendritic patterns in fluid flow in an anisotropic Hele-Shaw cell and measure the tip shapes and trajectories of individual dendritic branches under conditions where the pattern growth appears to be dominated by surface tension anisotropy and also under conditions where kinetic effects appear dominant. In each case, the tip position depends on a power law in the time, but the exponent of this power law can vary significantly among flow realizations. Averaging many growth exponents α yields bar α=0.64± 0.09 in the surface tension dominated regime and bar α=0.66±0.09 in the kinetic regime. Restricting the analysis to realizations when α is very close to 0.6 shows great regularity across pattern regimes in the coefficient of the temporal dependence of the tip trajectory. copyright 1996 The American Physical Society